XAFS data of native TBADH has been collected on zinc and cobalt K-edges. Analysis of EXAFS and edge data of native enzyme and its metal derivatives will provide the ground base for the assignment of coordination environment and accurate metal-ligand distances at the active site. Inhibition Studies: XAFS measurements on inhibited TBADH were conducted using TBADH-DMSO (dimethyl sulfoxide) complex. DMSO is known to inhibit ALDH in a transition state manner. X-ray crystallography studies of ALDH-DMSO complexes show that the DMSO ligand is directly bound to the catalytic zinc ion. XAFS and edge data will be collected on native TBADH and Cd/Co substituted TBADH complexed with DMSO. Assigning the coordination environment and metal-ligand distances of the active site in TBADH-DMSO complex will provide the structure of the transition state analogue of TBADH and a relevant structural intermediate in the catalytic pathway. SCIENTICIC SUBPROJECT 60